A “half-solution”…
Nextcloud 18 (with File Lock app installed) and OnlyOffice
Create a Group Folder.
Put the document inside and lock it (extend the 30-min default lockup period)
Everyone in the group can open it but is forced to save as a copy…
Downside:
If copies are saved into the same location as the (locked) original, it is readable by others.
If copies are saved to users’ own space/folder, it has to be shared with admin…
Never tested it, but I wonder if you could use flows.
When the teachers moves a file in a specific folder, the files is copied all the directories of the single students. Each student has his/her own copy of the file in a directory shared with him/her.
Maybe, if possible, you could do also the second passage: when a student tags the file as “done”, the same file is copied back in another directory with a name change that says which student did it…